Abstract
A large number of apple varieties (35) from the same germplasm were investigated over two consecutive harvest years. A total of 39 volatile compounds were identified by HS-SPME-GC-MS, and quantified by external standards. Principal component analysis was applied to study the relationship between varieties and volatiles. To obtain better discrimination, 23 of 35 apple varieties were classified into four cultivars and good classification could be observed by partial least squares discriminant analysis. Ethyl 2-methylbutyrate, 2-methyl-1-butanol, Z-3-hexenyl acetate, E-2-hexen-1-ol, linalool and dodecanol were the most important variables to discriminate apple cultivars. Based on the volatile concentration and thresholds, ethyl 2-methylbutyrate, hexanal, 1-hexanol, E-2-nonenal and linalool were the critical characterized odor-active compounds among 35 apple varieties over two harvest years. From the present work, seasonal effects greatly influenced the formation of volatiles.
Highlights
Aroma is an apple quality attribute consisting of one critical component but a complex mixture of volatiles which relies on volatile compounds, their concentrations and odor thresholds
23 of 35 apple varieties were classified into four cultivars and good classification could be observed by partial least squares discriminant analysis
In order to lower the loss of volatiles, all the apples were treated with liquid nitrogen after pre-treatment and stored in a −80 ◦C refrigerator, and all tests were completed within one month
Summary
Aroma is an apple quality attribute consisting of one critical component but a complex mixture of volatiles which relies on volatile compounds, their concentrations and odor thresholds. Most of the volatiles are classified into esters (78–92% of total volatiles), alcohols (6–16% of total volatiles), aldehydes and ketones [2]. The compositions and concentrations of volatiles are affected by many factors, including stage of maturity [3–5], storage conditions [3], climates [6] and terroir effect [7]. The concentrations of aldehydes decrease during the apple ripening period, while esters and alcohols become the main volatiles with their concentrations increasing [8]. Apple variety is another key factor that has a great influence on volatiles. Studies on various varieties reveal many differences both in volatiles’ composition and concentration [4,9–11]
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